For transfusions of blood and blood components, whole blood from a single donor is typically separated into three components: plasma, red blood cells and platelets. Each component may be used to treat a multiplicity of specific conditions and disease states. For example, the red blood cell component may be used to treat anemia and replace red blood cell loss due to bleeding, the concentrated platelet component may be used to control bleeding, and the plasma component may be given to patients to increase blood volume, or may be separated off-line after collection into individual plasma proteins such as fibrinogen, von Willebrand factor, Factor VIII, Factor IX, Anti-thrombin III, Fibrin sealant, thrombin, Alpha I and IVIG. Plasma from multiple donors may also be collected and combined or pooled together, and the combined plasma pool fractionated into the desired plasma proteins.
The separation of the collected plasma component into various protein or plasma components or fractions is called plasma fractionation. Such fractionation is typically done by large scale fractionators which combine plasma from many donors and concentrate individual plasma proteins by using the known techniques of cold alcohol fractionation (also known as Cohn fractionation) and chromatography.
There are traditionally two ways to obtain separated blood components from single donors. One way is to collect whole blood from donors and separate it into components at some time period after the whole blood collection. Using this method, whole blood is collected into approved containers that are pyrogen-free and sterile, and contain sufficient anticoagulant for the quantity of blood to be collected. Whole blood which is collected in this way is separated into components in a lab by a technician, and separation typically occurs from between about 2 and 8 hours after collection in the United States, and between about 2 to 24 hours in Europe.
Another way to separate whole blood into components is by using an apheresis device. These apheresis devices separate whole blood from a single donor, connected on-line to the device, into components automatically, and return any uncollected and unneeded blood components back to the donor during the collection procedure.
Apheresis devices may be used to separate the plasma component from the cellular components of a blood donation. Apheresis devices permit more frequent donations by a single donor due to the return of uncollected components.